linux-kernel - Re: [PATCH] intel-iommu: Turn off translations at shutdown

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Message-ID: <1672a5861c82c2e3c0c54b5311fd413a8eee5e64.camel@infradead.org>
Date:   Fri, 08 Nov 2019 07:54:17 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Deepa Dinamani <deepa.kernel@...il.com>, joro@...tes.org,
        linux-kernel@...r.kernel.org
Cc:     iommu@...ts.linux-foundation.org, Jason.Zeng@...el.com,
        "Tian, Kevin" <kevin.tian@...el.com>
Subject: Re: [PATCH] intel-iommu: Turn off translations at shutdown

On Thu, 2019-11-07 at 12:59 -0800, Deepa Dinamani wrote:
> The intel-iommu driver assumes that the iommu state is
> cleaned up at the start of the new kernel.
> But, when we try to kexec boot something other than the
> Linux kernel, the cleanup cannot be relied upon.
> Hence, cleanup before we go down for reboot.
> 
> Keeping the cleanup at initialization also, in case BIOS
> leaves the IOMMU enabled.
> 
> I considered turning off iommu only during kexec reboot,
> but a clean shutdown seems always a good idea. But if
> someone wants to make it conditional, we can do that.

This is going to break things for the VMM live update scheme that Jason
presented at KVM Forum, isn't it?

In that case we rely on the IOMMU still operating during the
transition.


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